Atmospheric plasma is a plasma to be generated with an electric discharge under an atmospheric pressure. The atmospheric plasma is utilized in a variety of technologies, such as disinfection, bacterial killing, antisepsis, gas decomposition, and material surface plasma-modification, and is broadly used for generation of ozone to be used for various sterilization, water purification technologies using ozone, sterilization technologies using oxygen plasma in a medical field, and more. As plasma generation devices for generating atmospheric plasma, a conductive electrode such as metal, and a dielectric electrode on the surface of which is laminated with a dielectric material are mainly used. In a variety of needs including the uses described above, a high-quality atmospheric plasma generation technology for stably generating plasma without being localized at a certain area is demanded. As for a conventional plasma generation device, there is a technique in which a solid dielectric member is provided on at least one facing surface of a pair of electrodes facing each other to adsorb and fix an object to be treated, thereby carrying out uniform plasma treatment on the object to be treated (refer to, for example, Patent Document 1). And, there is a technique in which a recess serving as a space for injecting a dielectric material therein is provided at the center of an upper electrode for an etching device, and the dielectric material is supplied into the recess depending on an in-plane distribution of electric field intensity of plasma to be generated, thereby uniformizing the in-plane distribution of the electric field intensity (refer to, for example, Patent Document 2). Also, as for a conventional plasma generation device, there is a technique in which a first electrode to which a discharge voltage is applied from a power supply unit, a dielectric material which is spaced apart from the first electrode with a predetermined interspace and surrounds the first electrode, a liquid dielectric material to be filled in the interspace between the first electrode and the dielectric material, and a second electrode disposed to be spaced apart from the dielectric material with a predetermined interspace are provided, thereby suppressing excess plasma generated at areas such as gaps between the electrodes and boundary regions around the electrodes (refer to, for example, Patent Document 3). Further, there is a technique in which an object gas to be treated and a carrier gas are passed through the inside of an inner tube of a double tubular dielectric material, a conductive liquid to be passed through between the inner tube and an outer tube is served as an outer electrode, blade parts are arranged, and a conductive continuous coil laid at a longitudinal outer circumference area of the blade parts is served as an inner electrode, thereby carrying out treatment on the object gas to be treated passing through the inside of the inner tube (refer to, for example, Patent Document 4).
As described above, a device for generating uniform plasma on an object to be treated, a device for suppressing generation of excess plasma due to a configuration in which an electrode is immersed in a liquid, a device for generating plasma so as to efficiently carry out treatment on an object gas to be treated, have been proposed as conventional plasma generation devices.